To manufacture laminated ceramic electronic components such as laminated ceramic capacitors, a process is carried out for forming a conductive paste film, which will serve as an internal electrode, onto a ceramic green sheet, for example. There is demand for the internal electrode obtained from this conductive paste film to have a high pattern accuracy and a uniform thickness. Gravure printing has garnered attention as a technique capable of meeting such demand.
Gravure printing is a printing method carried out using a gravure cylinder as a gravure printing plate, where a plurality of image sections, each configured as a collection of small recess-shaped cells, are formed in an outer circumferential surface of the gravure cylinder, and ink with which each cell is filled is transferred onto a printing target material.
An etching technique such as chemical etching, for example, is employed to form the image sections. The gravure cylinder can be manufactured efficiently, with a high machining accuracy, by employing an etching technique in this manner.
However, the following problems can arise when carrying out a process for forming a conductive paste film to serve as an internal electrode on a ceramic green sheet through gravure printing. Namely, because the image section formed in a gravure printing plate such as a gravure cylinder is configured of a collection of a plurality of cells, a contour in the conductive paste film transferred onto the ceramic green sheet, which serves as a printing target material, may not have the desired shape.
This will be described in further detail with reference to FIGS. 16A and 16B. FIG. 16A is an expanded view of part of the outer circumferential surface of a substantially drum-shaped gravure cylinder 1 that serves as a gravure printing plate, and illustrates the vicinity of an outer edge 3 of an image section 2. FIG. 16B, meanwhile, illustrates part of a ceramic green sheet 4 serving as a printing target material, and illustrates the vicinity of a contour 6 of a conductive paste film 5 transferred from the gravure cylinder 1. Note that the image section 2 illustrated here is designed so that the outer edge 3 thereof forms a straight line.
As shown in FIG. 16A, the banks 7, as well as a plurality of recess-shaped cells 8 and 9 defined by the banks 7, are provided in the image section 2 of the gravure cylinder 1. The cells 8 and 9 are divided into edge cells 8 located along the outer edge of the image section 2, and center cells 9 that are the remaining cells. The cells 8 and 9 are filled with a conductive paste, and the conductive paste in the cells 8 and 9 is transferred to the ceramic green sheet 4 during printing. The conductive paste film 5 is formed on the ceramic green sheet 4, as shown in FIG. 16B, as a result.
However, the contour 6 of the transferred conductive paste film 5 does not follow a straight line as designed, as can be seen in FIG. 16B. More specifically, the contour 6 has a substantially wave shape that matches the distribution of the edge cells 8. With the recent trend toward miniaturization and increased precision of laminated ceramic electronic components, it is extremely desirable to improve the linearity of the contour 6 of the conductive paste film 5.
The techniques disclosed in Japanese Unexamined Patent Application Publication No. 6-316174 and Japanese Unexamined Patent Application Publication No. 2006-51721, for example, have garnered attention as techniques that can meet the aforementioned demands to a certain extent.
FIGS. 17A and 17B are diagrams, corresponding to FIGS. 16A and 16B, respectively, that illustrate a gravure cylinder 1a and a conductive paste film 5a configured using the same basic concept as the technique disclosed in Japanese Unexamined Patent Application Publication No. 6-316174. In FIGS. 17A and 17B, elements that correspond to the elements shown in FIGS. 16A and 16B are given the same reference numerals, and redundant descriptions thereof will be omitted.
As shown in FIG. 17A, the banks 7 that define the plurality of cells 8 and 9 are prevented from reaching the outer edge 3 of an image section 2a, and a predetermined interval 10 is provided between the outer edge 3 and the banks 7 that face the outer edge 3. As a result, substantially frame-shaped recess portions 11 that extend continuously along the outer edge 3 are provided in the image section 2a. 
According to the gravure cylinder 1a that includes such an image section 2a, the contour 6 of the conductive paste film 5a will follow the outer edge 3 of the image section 2a in a precise manner, as shown in FIG. 17B, and as a result, the linearity of the contour 6 of the conductive paste film 5a is improved.
Nevertheless, the technique disclosed in Japanese Unexamined Patent Application Publication No. 6-316174 has the following problems to be solved.
Generally, when forming an image section on the outer circumferential surface of a gravure cylinder, a cylindrical base member configured of a metal is prepared, a plating layer is formed on the outer circumferential surface of the base member, and the image section, in which banks and cells are provided, is formed by partially removing the outer surface of the plating layer through chemical etching, for example.
With respect to the behavior of the etchant used in the chemical etching, it is easy for the etchant to accumulate in the predetermined interval 10 between the outer edge 3 and the banks 7 that face the outer edge 3 in the image section 2a shown in FIG. 17A; this makes it difficult for the etching to progress. Conversely, the etchant flows easily in areas comparatively far from the banks 7, such as in center areas of the edge cells 8, which makes it easy for the etching to progress.
As a result, arch portions 12 that curve outward are formed in the outer edge 3 of the image section 2a, in areas where the edge cells 8 are located, and as a result, the outer edge 3 takes on a shape in which comparatively large, continuous waves are present, as shown in FIG. 17A. For this reason, the contour 6 of the conductive paste film 5a formed on the ceramic green sheet 4 will also take on a shape in which comparatively large, continuous waves are present, as shown in FIG. 17B. While the linearity of the contour 6 of the conductive paste film 5a shown in FIG. 17B is better than the contour 6 of the conductive paste film 5a shown in FIG. 16B, it is necessary to reduce such waves to the greatest extent possible in the case where a higher degree of linearity is required.
Returning to the behavior of the etchant during chemical etching as mentioned earlier, it is known that widening the predetermined interval 10 in order to improve the flow of the etchant in the corresponding areas is effective as a way to improve the linearity of the outer edge 3 of the image section 2a. However, widening the predetermined interval 10 and by extension increasing the widths of the substantially frame-shaped recess portions 11 results in a problem that the required thickness cannot be obtained near the contour 6 of the conductive paste film 5a. This is because the transfer of the conductive paste starts from tips of the banks 7 that face the outer edge 3, and thus the amount of paste that is transferred drops due to the widening of the regions where the banks 7 are not present.
Meanwhile, FIG. 18 illustrates a gravure cylinder 1b configured using the same basic concept as the technique disclosed in Japanese Unexamined Patent Application Publication No. 2006-51721. FIG. 18 is a diagram corresponding to FIG. 16A or FIG. 17A. In FIG. 18, elements that correspond to the elements shown in FIG. 16A or FIG. 17A are given the same reference numerals, and redundant descriptions thereof will be omitted.
In an image section 2b of the gravure cylinder 1b shown in FIG. 18, the pitch at which the banks 7 extending toward the outer edge 3 are disposed is reduced, and the area of each of the edge cells 8 is reduced as a result. According to this gravure cylinder 1b, the degree of curvature in the arch portions 12 at the outer edge 3 of the image section 2b can be reduced by an amount corresponding to the reduction in pitch between the banks 7. Although not illustrated in the drawings, the degree of non-linearity in the contour of the transferred conductive paste film can be reduced as a result.
However, according to the gravure cylinder 1b described above, the edge cells 8 can be filled with a smaller amount of conductive paste. It is furthermore easier for the conductive paste to remain in the edge cells 8 during transfer due to the area of the opening of the edge cells 8 having dropped relative to the depth of the cells. Accordingly, like the gravure cylinder 1a shown in FIG. 17A, there is a problem that the required thickness cannot be obtained near the contour of the conductive paste film.
If the required thickness cannot be ensured near the contour of the conductive paste film, a further problem will appear in later steps in the manufacture of the laminated ceramic electronic component, such as firing, where metal particles present near the contour of the conductive paste film will be burned away and the surface area of the internal electrode will be reduced as a result. In a laminated ceramic capacitor, for example, this will lead to a problem in that the desired electrostatic capacity cannot be obtained.